1. Field of the Invention
This invention relates to a switchgear cabinet with an air-conditioning device having a heat exchanger, wherein air in the interior of the switchgear cabinet can be or is conducted to the heat exchanger and can be conditioned by the heat exchanger.
2. Description of Related Art
Switchgear cabinets of this type are known in many variations. Separate air-conditioners are installed on an outside of the switchgear cabinet for air-conditioning the interior of the switchgear cabinet are shown, for example, in German Patent Reference DE 197 12 474 C1 or German Patent Reference DE 196 09 794 C1. Air-conditioners which can mounted on the top are known from German Patent Reference DE 41 07 229 C2.
Customarily, the known air-conditioners have a coolant circuit, so that sufficient amounts of waste heat can be removed from the interior of the switchgear cabinet. Air-conditioners of this type have a relatively large energy consumption. If switchgear cabinets are placed in outside areas, batteries are often required for supplying current because of the lack of electrical connections, which must be maintained at regular intervals and possibly recharged.
It is one object of this invention to provide a switchgear cabinet of the type mentioned above but with efficient air-conditioning of the switchgear cabinet and with relatively little energy requirements.
In accordance with the invention this object is achieved with a heat exchanger that has an underground heat exchanger, which is placed into the ground.
In connection with the underground heat exchanger, use is made of a relatively constant temperature level (6xc2x0 C. to 11xc2x0 C.) which prevails in the ground, starting at a depth of approximately 1 m. Because the ground has a large storage capacity, particularly if it is moist, this heat storage can be effectively used for cooling the switchgear cabinet. Therefore, during summer operations of the switchgear cabinet and with permissible internal temperatures of, for example, 45xc2x0 C., there is an approximate temperature difference of 34xc2x0 Kelvin available to the underground heat exchanger. It is easily possible to achieve a high cooling output with this arrangement. In winter, when the temperature conditions are reversed, it is possible with a permissible internal temperature of 0xc2x0 C. to utilize a temperature difference of, for example, 6xc2x0 Kelvin for the underground heat exchanger. In this mode the underground heat exchanger operates as a heater.
The air contained in the interior of the switchgear cabinet can be conveyed by the underground heat exchanger. However, it is also possible to conduct various fluids through the underground heat exchanger. Accordingly, particular gases or liquids can be conveyed. An interior heat exchanger is assigned to the interior of the switchgear cabinet, particularly if gases or liquids are used. The fluid coming from the underground heat exchanger then circulates through this interior heat exchanger. For improving its efficiency, it is then possible to assign a fan to the heat exchanger.
In one embodiment which is particularly simple, the underground heat exchanger is connected to an inlet line and to an outlet line, wherein air coming from the interior of the switchgear cabinet can be supplied to the underground heat exchanger via the inlet line and wherein this air, which has been conditioned in the underground heat exchanger, can be returned, at least in part, to the interior of the switchgear cabinet through the outlet line after it has flowed through the underground heat exchanger. Because the supply of air from the switchgear cabinet is directly conveyed through the underground heat exchanger, only a few structural components are required.
In accordance with one preferred embodiment of this invention, the underground heat exchanger is embodied as a flexible plastic pipe. This entire plastic pipe can be placed into the ground in a simple and time-saving manner. It is thus possible to provide the outlet line and the inlet line connected in one piece with the underground heat exchanger and conducted as far as the area of the interior of the switchgear cabinet. This outlet line and the inlet line are connected to pipe connector elements leading into the interior of the switchgear cabinet. Because the outlet and the inlet lines are embodied as one piece with the underground heat exchanger, no additional assembly and parts outlay is required. It is possible to conduct the plastic pipe as far as the area of the interior of the switchgear cabinet, or it can be connected with appropriate pipe connectors.
In accordance with one embodiment of this invention, the underground heat exchanger is assembled from rigid pipe sections and pipe elbows. For example, pipe elements which are customary in plumbing technology can be used as rigid pipe sections and pipe elbows. They have a sufficient pressure resistance. Moreover, sufficient heat transfer can be assured at the pipe walls.
An effective heat exchange in the interior of the switchgear cabinet is possible if the outlet line forms a blow-in or aspirating opening in the roof area of the interior of the switchgear cabinet, and the inlet line conveys the conditioned air into the bottom area of the interior of the switchgear cabinet.
In accordance with one embodiment of this invention, at least one fan is assigned to the inlet line and/or the outlet line. The use of one or several fans makes a less noisy operation of the air-conditioner possible. This is possible if the interior of the switchgear cabinet is surrounded by a switchgear cabinet body, and each fan is housed in the interior of the switchgear cabinet. In this case no noise-generating elements of the air-conditioner are present outside the switchgear cabinet, such as is normally required with air-conditioners. The fans require relatively little electrical energy. In particular, the fans can be designed as direct current fans, which are directly supplied by a battery assigned to the interior of the switchgear cabinet.
Preferably, the underground heat exchanger is placed in a meander shape in the ground. Here, spaces are created between the individual loops formed by the meanders. In this case the loops must be spaced apart sufficiently far so that no mutual heat interference can occur.
In a switchgear cabinet in accordance with this invention, a switchgear cabinet body is fastened on a switchgear cabinet base and the cabinet body encloses the interior of the switchgear cabinet. The bottom group forms a seal between the base supporting the switchgear cabinet, for example a concrete base, and the actual switchgear cabinet body.
With this, depending on the design of the seal of the bottom group, moisture can be prevented from entering the interior of the switchgear cabinet. In some applications, the seal prevents rodents, for example, from entering the interior of the switchgear cabinet.
In accordance with this invention, the inlet lines and the outlet lines are closed off at the switchgear cabinet by air-permeable covers. This prevents objects, for example tools, from falling into the underground heat exchanger during assembly in the interior of the switchgear cabinet. This also prevents rodents, which can enter the pipe area of the underground heat exchanger, from also entering the interior of the switchgear cabinet.